This invention relates to self-steering mechanisms for boats and more particularly to a wind vane sensitive type of steering mechanism which controls a differential hydraulic pressure regulator that in turn will control the operation of a hydraulic motor attached to the rudder.
Autopilots and wind vane gears are the two broad classifications of existing self-steering equipment. There are a number of manufacturers of autopilots and of vane gears. The autopilots are battery operated, which makes them a good choice for power boats, but they cannot be considered to be a practical solution for the cruising sailboat.
There are currently four general types of vane gear systems.
1. Vane to Tiller - The vane is connected directly to the main rudder via the tiller. This system is used on small boats, or boats with a balanced rudder, or boats that have a light helm. PA1 2. Trim Tab - It can be hung independently aft but is usually pivoted on the trailing edge of the main rudder. The trim tab is controlled by the wind vane. The system can be used only on boats that have an outboard rudder. The tiller is left free. PA1 3. Auxiliary Rudder - A small rudder is hung on the stern and connected by linkage to the wind vane for control. This small rudder may have a trim tab control as per type 2. The boat's unbalance must be removed at the main rudder by securing the tiller or wheel. A change of tack, and possibly wind strength, would necessitate a readjustment at the tiller or wheel. This type cannot be used on boats having an outboard rudder because of the unpredictable water turbulence. PA1 4. Servo Pendulum - At the stern, the system consists of a wind vane controlling, through linkage, the angle of attack of a pendulum blade with the water. The blade is horizontally pivoted and its movement controls the main rudder via lines to the tiller or a drum mounted on the wheel. The linkage from the vane to blade is necessarily complicated. Also, when the rudder turns to put on weatherhelm, the pendulum blade has to rotate up towards the water surface, always on the windward side. This rotation is added to the heel angle resulting in the blade's lift falling drastically. PA1 1. In addition to picking up the direction of the apparent wind, the vane must also provide operational torque for turning and holding at an angle of attack the primary rudder, auxiliary rudder, trim tab, or pendulum blade. Therefore, one side of the vane is always working against the wind. This results in the vane angle varying with wind strength, which contributes to boat oscillations. On horizontal and inclined axis vanes, a small vane is needed for heavy weather, and a larger vane is needed for light airs. PA1 2. The relationship between the vane axis and the horizon varies with the boat heeling, thereby contributing to unsteady steering. The pitching at the stern, caused by the fore and aft motion of the boat, generates adverse rotary inertia at the counterweighted wind vane which also impairs steering. PA1 3. A movement of the water level up or down, due to the pitching, heeling, or rolling of the boat, changes the surface area of the tab, aux. rudder, or blade in contact with the water, thereby affecting the performance of these components and the consequent steering steadiness. PA1 4. The size of the tab, aux. rudder, or blade is related to its location, the primary rudder size, and the primary rudder location. Also, the size of the wind vane is related to the size of tab, aux. rudder, or blade. Sizing the self-steering system to a particular boat is not easy and would be a gamble for most boat owners. It could result in the boat being either oversteered or lack adequate steering control. PA1 5. Control lines and pulleys connect the steering unit to the tiller or drum on the wheel, which clutter the deck and cockpit. PA1 6. In many cases, it is not a simple operation to activate self-steering or change to manual operation. PA1 1. The wind vane need only provide a directional fix on the apparent wind. The operational torque required at the rudder shaft is created completely at the hydraulic pump. The wind vane will therefore weathercock easily and be responsive even in light airs. Variation of wind strength, as related to the vane, does not effect steering and only one size vane is required for all boat sizes and wind speeds. PA1 2. The hydraulic vane control unit, comprised of wind vane, pressure regulator, and water-driven pump, is pivoted at its stern support, thereby enabling the axis to always be perpendicular to the water surface, because of the counterweighted lower end. The vane remains upright, regardless of the boat heel angle. The pivot also keeps the pump well below the water surface at all times. PA1 3. Only one size of hydraulic vane control unit will handle all sailboats with a length of 20 to 50 feet, regardless of weather and boat characteristics. By controlling the main rudder, adequate steering capability is assured. The bore diameter of the hydraulic cylinder and the length of rudder arm are varied with the size of boat. The boats of greater length or displacement will require the larger cylinder bore and longer rudder arm, thereby providing greater torque at the rudder and a slower rudder movement, which is required for the larger boats. When used with an outboard rudder, the steering steadiness will not be affected by the water turbulence in the area of the pump. PA1 4. Below deck control of the rudder is provided, thus clearing the deck and cockpit of lines and pulleys. PA1 5. The steering unit can be easily pivoted to a near horizontal position and secured for racing, anchoring, and unfouling of the submerged parts. PA1 6. Activation of self-steering or changing to manual steering is easily accomplished, respectively, by releasing or securing a control line. PA1 1. It controls the oil pressure at either end of a double acting hydraulic cylinder, and thereby establishes the rudder angle. The pressure is varied by either a change of wind direction, boat heading, or water speed. PA1 2. It performs as a directional four way valve, determining whether the rudder angle is on the port side or starboard side, relative to the keel centerline.
Disadvantages that are common to all of the above wind vane gears are as follows:
The present invention exhibits the following advantages over the prior art: